This invention relates to trenching machines of both the wheel or the chain type.
The drawings illustrate a trenching machine of the wheel type which includes a pair of spaced apart circular rims mounted for rotational movement and including at their outer peripheral edges a plurality of excavating members for engaging the ground and excavating a trench. Certain problems have been encountered with trenching devices presently being used.
One problem pertains to the mounting of the circular rims for rotation. This is usually done by means of three wheels or dollies which rotatably engage the inner margins of the rims. Throughout extensive use of the trenching machine the inner margins of the rims begin to wear, and eventually there is substantial slack between the wheels and the rims Taking up of this slack is a cumbersome task.
Another problem encountered with present devices pertains to the excavating members which are on the outer peripheral edge of the rims. These excavating members in presently known devices are of the same cross-sectional shape as the bottom of the trench to be excavated. Because each excavating member is the same shape as the bottom of the trench, there is considerable friction and resistance encountered during the excavating process. Furthermore, when the excavating member reaches the top of the circle, there is a scraping member which scrapes the material from the excavating member and permits it to fall to a conveyor to be carried away. With presently known excavating members considerable resistance is encountered between the scraping member and the excavating members, thereby causing wear and tear on the machine parts.
Another problem encountered with present excavating devices pertains to the shoe assembly which is mounted rearwardly of the excavating wheel. The shoe assemblies generally include two spaced apart parallel plates adapted to follow behind the wheel and to engage the lateral sides of the trench rearwardly of the wheel. These plates must be sufficiently rigid to provide reinforcement of the lateral walls of the trench immediately behind the wheel, but at the same time, they must be sufficiently flexible to permit the wheel to change directions as it is excavating the trench.
Another problem with the shoe assembly of the present devices pertains to the elongated shoe which is approximately horizontally disposed and which follows along on the bottom of the trench immediately behind the wheel. The horizontal attitude of this shoe must be adjusted slightly depending upon the particular soil configuration which is being excavated. Adjusting the attitude of this shoe has heretofore been a time-consuming and complicated problem.